In typical, a storage apparatus includes a disk array of magnetic disk drives or flash memory devices and a storage controller for controlling data transfer between the disk array and a host computer. The storage controller includes a host interface of a device for connecting to the host computer, a drive interface of a device for connecting to the disk array, a primary storage device including a cache area used to store data frequently referenced by the host computer or data to be transferred, and a processor.
These components may be duplicated to increase the availability of the storage apparatus. In such a case, a set of the components is referred to as a cluster and clusters may be interconnected with a dedicated interface. For example, JP 2010-033125 A (PTL 1) discloses a technique to access a cache area retaining requested data in a cluster from a host interface in a different cluster to which a host computer is connected, in a storage system including a storage-dedicated LSI.
Another document, PCI-Express Base Specification Revision 3.0 (NPL 1), discloses the following technique as a standard technology for PCI-Express, which is a specification for a general-purpose interface: When a PCI device transmits data to a processor, the PCI device attaches information indicating the expected frequency of reference and the characteristics of data called transaction layer packet processing hint (TPH) to the data; the processor refers to the TPH and stores data determined that will be referenced with high frequency to a cache memory built in the processor.